Drying of Droplets Containing Insoluble Nanoscale Particles: Second Drying Stage

A theoretical model describing the second drying stage of a droplet containing a liquid with insoluble nanoscale primary particles is presented. The model enables two possible pathways for the evolution of the particle morphology, leading to the formation of either a full solid particle or a hollow particle containing internal aggregates. It was found that the final morphology of the dry particle depends on the size of the suspended primary particles, the strength of the particle crust, the initial moisture content, and the parameters of the drying agent. The formation of a hollow particle morphology is more likely for smaller primary particles and stronger inter-particle forces.